Photoresist composition for forming an insulation film, insulation film for organic electroluminescence element and method for itis formation

ABSTRACT

A photoresist composition comprising (A) a resin soluble in an alkali, (B) an ester of a quinonediazidesulfonic acid, (C) a thermosetting component and an organic solvent; an insulation film for organic EL devices which is formed by heating a resist film formed with the composition on a substrate in accordance with photolithography, has a sectional shape having upper edge portions having a round shape and the width increasing towards the bottom portion and has a thickness is in the range of 0.3 to 3 μm; and a process for producing the insulation film using the photoresist composition. The photoresist composition, the insulation film for organic EL devices and the process for producing the insulation film provide an insulation film having a sectional shape advantageous for an insulation film for organic EL devices since the width in the sectional shape of the film increases towards the bottom portion.

TECHNICAL FIELD

[0001] The present invention relates to a photoresist composition forforming an insulation film, an insulation film for organicelectroluminescence devices (electroluminescence will be referred to asEL, hereinafter), a process for producing the insulation film and anorganic EL device comprising the insulation film. More particularly, thepresent invention relates to a positive-type photoresist compositionused for forming an insulation film for organic EL devices having asectional shape having the width increasing towards the bottom portion,an insulation film for organic EL devices which is formed by using thephotoresist composition and has a sectional shape having the widthincreasing towards the bottom portion, a process for efficientlyproducing the insulation film with the above photoresist composition,and an organic EL device comprising the insulation film having asectional shape having the width increasing towards the bottom portion.

BACKGROUND ART

[0002] EL devices which utilize light emission under application of anelectric field show high self-distinguishability due to theself-emission and exhibit excellent impact resistance since they arecompletely solid devices. Therefore, EL devices have been attractingattention for application as light emitting devices in various types ofdisplay apparatus.

[0003] The EL devices include inorganic EL devices in which an inorganiccompound is used as the light emitting material and organic EL devicesin which an organic compound is used as the light emitting material.Organic EL devices have been extensively studied for practicalapplication as a light emitting device of the next generation since theapplied voltage can be decreased to a great extent, the size of thedevice can be reduced easily, consumption of electric power is small,planar light emission is possible and three primary colors are easilyemitted.

[0004] As for the construction of the organic EL device, the basicconstruction comprises a transparent electrode layer (an anode), a layerof a thin film of an organic light emitting material (an organic lightemitting layer) and a metal electrode layer (a cathode), which aresuccessively formed on a transparent substrate. Constructions having ahole injecting and transporting layer or an electron injecting layersuitably added to the basic construction are known. Examples of suchconstructions include the construction of an anode/a hole injecting andtransporting layer/an organic light emitting layer/a cathode and theconstruction of an anode/a hole injecting and transporting layer/anorganic light emitting layer/an electron injecting layer/a cathode. Thehole injecting and transporting layer has the function of transportingholes injected from the anode. The electron injecting layer has thefunction of transporting electrons injected from the cathode to thelight emitting layer. It has been known that, due to the hole injectingand transporting layer disposed between the light emitting layer and theanode, a greater amount of holes are injected into the light emittinglayer under a lower electric field and electrons injected into the lightemitting layer from the cathode or the electron injecting layer areaccumulated at the interface between the hole injecting and transportinglayer and the light emitting layer to increased the efficiency of thelight emission since the hole injecting and transporting layer does nottransport electrons.

[0005]FIG. 1 shows a diagram exhibiting the principle of an example ofthe organic EL device. As shown in this Figure, an organic EL devicehas, in general, a construction in which an organic EL material layer 5comprising a hole injecting and transporting layer 7, an organic lightemitting layer 8 and an electron injecting layer 9 is laminated to atransparent electrode (the anode) 2 disposed on a transparent substrate1 and a metal electrode layer (the cathode) 6 is further laminated tothe organic EL material layer 5. When an electric current is appliedbetween the anode and the cathode, light is generated in the organiclight emitting layer 8 and emitted to the outside through thetransparent substrate in the above construction.

[0006] For preparing the organic EL device, a patterned transparentelectrode (the anode) is formed on a transparent substrate such as aglass plate in accordance with the vapor deposition or the sputteringand an insulation film having a desired pattern is formed on the formedtransparent electrode. The insulation film can be formed, for example,in accordance with the etching of a film of a polyimide resin or thelithography using a photoresist. The insulation film may be used also asthe light-shielding film.

[0007] On the insulation film formed on the transparent substrate, aresist pattern layer having a rectangular sectional shape or a undercutpattern profile is formed in accordance with the lithography. The formedresist pattern layer can be used as a resin separation layer and aplurality of such layers may be formed. For example, a hole injectingand transporting layer, an organic light emitting layer and an electroninjecting layer are successively formed between the resin separationlayers in accordance with the vacuum vapor deposition so that an organicEL material layer is formed. A metal electrode layer (the cathode) isfurther laminated on the formed organic EL material layer and a lightemitting portion is formed. A sealing layer is formed on the lightemitting portion in the final step and a sealed organic EL device isobtained.

[0008]FIG. 2 shows a partial sectional view exhibiting the constructionof an example of the light emitting portion in a conventional organic ELdevice. On a transparent substrate 1 having a patterned transparentelectrode 2, resist pattern layers (resin separation layers) 4 having anundercut pattern profile is disposed via insulation films 3. Between theresist pattern layers, an organic EL material layer 5 (having aconstruction constituted with a hole injecting and transporting layer,an organic light emitting layer and an electron injecting layer whichare formed successively from the side of the transparent electrodelayer) having a metal electrode layer 6 on the surface is disposed.Thus, a light emitting portion is formed independently withoutcontacting the resist pattern layers 4. On the resist pattern layer 4,an organic EL material layer 5 a having a metal electrode layer 6 a onthe surface is formed due to convenience in the preparation although theorganic EL material layer 5 a is not necessary from the standpoint ofthe function.

[0009] The insulation film 3 in the organic EL device having theconstruction described above has, in general, a rectangular sectionalshape as shown in FIG. 2. However, in the formation of the organic ELmaterial layer on the transparent electrode 2 between the resinseparation layers 4 and the light emitting portion by laminating a metalelectrode (the cathode) on the organic EL material layer in accordancewith the vacuum vapor deposition, it is difficult that the side faces ofa light emitting portion are formed in a vertically flat shape due tothe characteristic of the vacuum vapor deposition when the sectionalshape of the insulation film is rectangular. Occasionally, the lightemission becomes uneven due to the extended deposition of the metalelectrode material on the side faces during the vapor deposition of themetal electrode layer or short circuit takes place due to attachment ofthe metal electrode material to the transparent electrode. Therefore, aproblem arises in that the frequency of the formation of defect productsincreases.

[0010] To overcome the above problem, it is considered that a sectionalshape having upper edge portions having a round shape and a widthincreasing towards the bottom portion is advantageous. When theinsulation film has the sectional shape described above, the extendeddeposition of the metal electrode material on the side faces issuppressed during the vapor deposition.

[0011] In accordance with a recently developed technology, a pattern isformed with a plurality of holes having a transparent electrode layerexposed at the bottom portion, a polymer organic EL material is injectedthrough nozzles into the holes in accordance with the ink-jet process toform organic EL material layers in the holes, and a metal electrodelayer is laminated on the formed layers to prepare an organic EL device.In this technology, banks composed of an insulation film (which alsoworks as the light-shielding film) is disposed between the holes. Forthis insulation film, the sectional shape having upper edge portionshaving a round shape and a width increasing towards the bottom portionis considered to be more advantageous than the rectangular sectionalshape.

[0012] Under the above situation, the present invention has an object ofproviding a photoresist composition which is advantageously used as theinsulation film for organic EL devices and provides an insulation filmhaving the sectional shape having upper edge portions having a roundshape and the width increasing towards the bottom portion, an insulationfilm for organic EL devices which is obtained by using the abovecomposition and has the sectional shape having the width increasingtowards the bottom portion, a process for efficiently producing theinsulation film and an organic EL device having the insulation filmhaving the sectional shape having the width increasing towards thebottom portion.

DISCLOSURE OF THE INVENTION

[0013] As the result of intensive studies by the present inventors toachieve the above object, it was found that a positive-type photoresistcomposition comprising a thermosetting component which was cured at aspecific temperature was suitable for the object of forming theinsulation film having the sectional shape having upper edge portionshaving a round shape and the width increasing towards the bottomportion, and that an insulation film for organic EL devices having thedesired sectional shape having the width increasing towards the bottomportion could be obtained by forming a resist film having a desiredpattern with the above composition in accordance with thephotolithography, followed by heating the formed resist film at aspecific temperature. The present invention has been completed based onthis knowledge.

[0014] The present invention provides:

[0015] (1) A photoresist composition for forming an insulation film fororganic electroluminescence devices which comprises (A) a resin solublein an alkali, (B) an ester of a quinonediazidesulfonic acid, (C) athermosetting component which is cured at a temperature higher than atemperature of heat resistance of a resist film formed with thecomposition in accordance with photolithography, and an organic solvent;

[0016] (2) A photoresist composition for forming an insulation filmdescribed in (1), wherein the thermosetting component of component (C)is a thermosetting imide resin represented by general formula [1]:

[0017]  wherein R represents a group expressed by:

[0018]  representing an integer of 3 to 8;

[0019] (3) A photoresist composition for forming an insulation filmdescribed in any one of (1) and (2), which comprises 1 to 20 parts byweight of component (C) per 100 parts by weight of component (A);

[0020] (4) An insulation film for organic electroluminescence deviceswhich is formed by heating a resist film having a desired pattern andformed with a composition described in any one of (1), (2) and (3) on asubstrate in accordance with photolithography, has a sectional shapehaving upper edge portions having a round shape and a width increasingtowards a bottom portion and has a thickness in a range of 0.3 to 3 μm;

[0021] (5) A process for producing an insulation film for organicelectroluminescence devices described in (4), the process comprisingforming a resist film having a substantially rectangular sectional shapeand a desired pattern with a photoresist composition described in anyone of (1), (2) and (3) on a substrate in accordance withphotolithography and heating the formed resist film at a temperaturehigher than a temperature of heat resistance of the resist film so thatthe thermosetting component in the resist film is cured; and

[0022] (6) An organic electroluminescence device which comprises aninsulation film described in (4).

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 shows a diagram exhibiting the principle of an example ofthe organic EL device.

[0024]FIG. 2 shows a partial sectional view exhibiting the constructionof an example of the light emitting portion in a conventional organic ELdevice.

[0025]FIG. 3 shows a diagram exhibiting an example of the change in theshape when the resist film formed in accordance with thephotolithography is heated in the preparation of the insulation film ofthe present invention.

[0026]FIG. 4 shows a partial sectional view exhibiting the constructionof an embodiment of the light emitting portion in the organic EL deviceof the present invention.

[0027] In the Figures, 1 means a transparent substrate, 2 means atransparent electrode layer, 3 and 3′ mean insulation films, 4 means aresist pattern layer having a undercut pattern profile, 5 and 5 a meanorganic EL material layers, 6 and 6 a mean metal electrode layers, 7means a hole injecting and transporting layer, 8 means an organic lightemitting layer and 9 means an electron injecting layer.

THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION

[0028] The photoresist composition for forming an insulation film oforganic EL devices of the present invention (this composition will beoccasionally referred to as the photoresist composition of the presentinvention) will be described in the following.

[0029] The photoresist composition of the present invention is aphotoresist composition comprising (A) a resin soluble in an alkali, (B)an ester of a quinonediazidesulfonic acid, (C) a thermosetting componentand an organic solvent.

[0030] The resin soluble in an alkali of component (A) is notparticularly limited and a suitable resin can be selected as desiredfrom resins soluble in an alkali which are conventionally used forpositive-type photoresists comprising esters of quinonediazidesulfonicacids as the photosensitive agent. Examples of the resin soluble in analkali include condensation products of phenols and aldehydes or ketones(novolak resins), vinylphenol-based polymers, isopropenylphenol-basedpolymers and hydrogenation products of these phenol resins. Examples ofthe phenol used as the material for the condensation products of phenolsand aldehydes or ketones include monohydric phenols such as phenol,o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 3,5-xylenol,2,6-xylenol, 1,2,3-trimethylphenol, 2,3,4-trimethylphenol,2,3,5-trimethylphenol, o-ethylphenol, m-ethylphenol, p-ethylphenol,o-propylphenol, m-propylphenol, ppropylphenol, o-butylphenol,m-butylphenol, p-butylphenol, o-phenylphenol, m-phenylphenol,p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol and3-methylmethoxyphenol; and polyhydric phenols such as resorcinol,pyrocatechol, hydroquinone, bisphenol A, phloroglucinol and pyrogallol.

[0031] Examples of the aldehyde include formaldehyde, paraformaldehyde,benzaldehyde, hydroxybenzaldehyde, terephthalaldehyde, acetaldehyde andhydroxyacetaldehyde. Examples of the ketone include acetone, methylethyl ketone, diethyl ketone and diphenyl ketone.

[0032] The condensation product can be obtained in accordance with aconventional process, for example, comprising reacting a phenol and analdehyde or a ketone in the presence of an acidic catalyst.

[0033] The vinylphenol-based polymers are selected from the homopolymerof vinylphenol and copolymers of vinylphenol with componentscopolymerizable with vinylphenol. The isopropenylphenol-based polymersare selected from the homopolymer of isopropenylphenol and copolymers ofisopropenylphenol with components copolymerizable withisopropenylphenol. Examples of the component copolymerizable withvinylphenol or isopropenylphenol include acrylic acid, methacrylic acid,styrene, maleic anhydride, maleimide, vinyl acetate, acrylonitrile andderivatives of these compounds. The copolymers can be obtained inaccordance with a conventional process.

[0034] The hydrogenation product of the phenol resin can be obtained inaccordance with a conventional process such as the process comprisingdissolving the above phenol resin into an organic solvent, followed byhydrogenating the dissolved resin in the presence of a homogeneouscatalyst or a heterogeneous catalyst.

[0035] The resin soluble in an alkali having the molecular weight andthe molecular weight distribution controlled by a conventional means canalso be used. Examples of the means for controlling the molecular weightand the molecular weight distribution include pulverizing the resin,followed by subjecting to the solid-liquid extraction with an organicsolvent having a suitable solubility; dissolving the resin into a goodsolvent, followed by adding the resultant solution dropwise into a poorsolvent; and adding a poor solvent to the resin, followed by subjectingthe resulting product to the solid-liquid extraction or theliquid-liquid extraction.

[0036] The resin soluble in an alkali of component (A) may be usedsingly or in combination of two or more. In the present invention,phenol-based novolak resins soluble in an alkali obtained bypolycondensation of a phenol and an aldehyde in the presence of an acidcatalyst are preferable among the above resins soluble in an alkali.Cresol novolak resins soluble in an alkali obtained by using a mixedcresol comprising m-cresol and p-cresol as the phenol are morepreferable.

[0037] In the present invention, it is advantageous that the resinsoluble in an alkali of component (A) is selected so that the resistfilm formed by using the photoresist composition comprising the resin inaccordance with the photolithography has a thermal property such thatthe temperature of heat resistance is, in general, in the range of 90 to130° C. and preferably in the range of 95 to 125° C.

[0038] The temperature of heat resistance is the value measured inaccordance with the following method.

[0039] A photoresist composition is applied to a silicon wafer and driedand a resist film having a thickness of 1.2 μm is formed. A pattern oflines and spaces of 10 μm is formed through a mask. The resultantproduct is heated for 5 minutes on a hot plate, and the width of thelines is measured. The temperature at which the width of the linesexceeds 120% of the width before being heated is used as the temperatureof heat resistance.

[0040] In the photoresist composition of the present invention, theester of a quinonediazidesulfonic acid used as component (B) is notparticularly limited and a suitable compound can be selected as desiredfrom esters of quinonediazidesulfonic acids conventionally used as thephotosensitive agent. Examples of the ester of a quinonediazidesulfonicacid include compounds obtained by converting a specific fraction of thephenolic hydroxyl group in polyphenol compounds into esters of1,2-naphthoquinonediazide-5-sulfonic acid, esters of1,2-naphthoquinonediazide-4-sulfonic acid, esters of1,2-naphthoquinonediazide-6-sulfonic acid, esters of1,2-benzoquinonediazide-5-sulfonic acid and esters of1,2-benzoquinonediazide-4-sulfonic acid. Among these compounds, estersof 1,2-naphthoquinonediazide-5-sulfonic acid and esters of1,2-naphthoquinonediazide-4-sulfonic acid are preferable and esters of1,2-naphthoquinonediazide-4-sulfonic acid are more preferable. A resistcomposition exhibiting an excellent balance between the sensitivity andthe resolution can be provided by using the ester of1,2-naphthoquinonediazide-4-sulfonic acid.

[0041] The polyphenol used for the above compounds is a compound havingtwo or more, preferably three or more and more preferably four or morephenolic hydroxyl groups. Examples of the polyphenol includepolyhydroxybenzophenones such as 2,3,4-trihydroxybenzophenone,2,4,4′-trihydroxybenzophenone, 2,3,4,4′-tetrahydroxybenzophenone,2,4,2′, 4′-tetrahydroxybenzophenone and2,3,4,2′,4′-pentahydroxybenzophenone; polyhydroxytrisphenylalkanes suchas tris(4-hydroxyphenyl)methane,1,1,1-tris(4-hydroxy-3-methylphenyl)ethane,1,1,1-tris(4-hydroxy-3-methylphenyl)ethane,1,1,1-tris(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxy-3-methylphenyl)-1,1-(4-hydroxyphenyl)ethane andbis(4-hydroxy-3-methylphenyl)-2-hydroxy-4-methoxyphenylmethane; trimersof phenols and formaline; tetramers of phenols and formaline; andnovolak resins. The polyphenol is not limited to the compounds describedas the examples.

[0042] Esters of quinonediazidesulfonic acids obtained by using tri- ortetrahydroxybenzophenone as the polyphenol are preferable sinceexcellent sensitivity and resolution are provided.

[0043] The process for preparing the ester is not particularly limited.The ester can be obtained by reacting the quinonediazidesulfonic acidhalide and preferably the quinonediazidesulfonic acid chloride with thepolyphenol compound in accordance with a conventional process in asolvent such as acetone, dioxane and tetrahydrofuran in the presence ofan inorganic base such as sodium carbonate, sodium hydrogencarbonate,sodium hydroxide and potassium hydroxide or an organic base such astrimethylamine, triethylamine, tripropylamine, diisopropylamine,tributylamine, pyrrolidine, piperidine, piperadine, morpholine, pyridineand dicyclohexylamine.

[0044] In the ester used in the present invention, the fraction ofhydroxyl group of the polyphenol converted into the ester of aquinonediazidesulfonic acid (the average fraction of esterification) isthe value calculated from the amount by equivalent of hydroxyl group ofthe polyphenol and the amount by mole of the quinonediazidesulfonic acidhalide used for the reaction. The average fraction of esterification is,in general, 60% or greater and preferably 65% or greater. The upperlimit of the average fraction of esterification is, in general, 100% andpreferably 90%. When the average fraction is 60% or greater, the shapeof the pattern and the resolution can be improved.

[0045] In the present invention, the ester of a quinonediazidesulfonicacid of component (C) may be used singly or in combination of two ormore. It is advantageous that the content of the ester of1,2-naphthoquinonediazide-5-sulfonic acid is controlled at 20% by weightor smaller and preferably at 10% or smaller in the entire photosensitiveagents.

[0046] In the photoresist composition of the present invention, thecontent of the ester of a quinonediazidesulfonic acid of component (C)is selected, in general, in the range of 1 to 50 parts by weight andpreferably in the range of 10 to 30 parts by weight per 100 parts byweight of the resin soluble in an alkali of component (A). When thecontent of component (C) is in the above range, the photoresistexhibiting an excellent balance between the properties of the resistsuch as the effective sensitivity, the fraction of the residual film andthe resolution can be obtained.

[0047] As the thermosetting component of component (C) in thephotoresist composition of the present invention, a thermosettingcomponent which is cured at a temperature higher than the temperature ofheat resistance of a resist film formed with the composition inaccordance with photolithography is used. When the curing temperature ofthe thermosetting component is lower than the temperature of heatresistance of the resist film, the insulation film having the desiredsectional shape having the width increasing towards the bottom portioncannot be obtained. It is preferable that the temperature of the startof the curing is higher than the temperature of heat resistance of theresist film by 5° C. or greater and more preferably by 10° C. orgreater. When the temperature of the start of the curing is excessivelyhigher than the temperature of heat resistance of the resist film, thewidth of the sectional shape increases excessively towards the bottomportion and an insulation film having the desired sectional shape cannotbe obtained. Therefore, it is preferable that the temperature of thestart of the curing is higher than the temperature of heat resistance ofthe resist film by 50° C. or lower and more preferably by 30° C. orlower.

[0048] The thermosetting component of component (C) is not particularlylimited as long as the component has the temperature of the start of thecuring within the above range and the insulating property of theobtained film is not adversely affected. Various thermosetting compoundssuch as epoxy resins, guanamine resins, phenol resins, unsaturatedpolyester resins, imide resins, polyurethanes, maleic acid resins,melamine resins and urea resins can be used. Among these compounds,imide resins are preferable and thermosetting imide resins are morepreferable. Examples of the thermosetting imide resin includebisallylnadimides represented by general formula [1]:

[0049] wherein R represents a group expressed by:

[0050] representing an integer of 3 to 8. The bisallylnadimide is curedby heating and exhibits excellent heat resistance.

[0051] The thermosetting component of component (C) may be used singlyor in combination of two or more. The content of component (C) in thephotoresist composition is selected, in general, in the range of 1 to 20parts by weight and preferably in the range of 3 to 15 parts by weightper 100 parts by weight of the resin soluble in an alkali of component(A) from the standpoint of the effect.

[0052] To provide the formed insulation film with the function of thelight-shielding film, where desired, the photoresist composition of thepresent invention may further comprise at least one light-shieldingmaterial selected from carbon black, chromium oxide, iron oxide,titanium black, aniline black, black organic pigments and mixed organicpigments having quasi-black color obtained by mixing at least twoorganic pigments selected from red, blue, green, violet, yellow, cyanand magenta.

[0053] It is preferable that the light-shielding material is containedin the photoresist composition in an amount of 20 to 80% by weight.Among the above light-shielding materials, titanium black is preferablefrom the standpoint of the light-shielding property.

[0054] To enhance the sensitivity, where desired, the photoresistcomposition of the present invention may further comprise phenolcompounds such as polyhydroxybenzophenones described above,1-[1-(4-hydroxyphenyl)isopropyl]-4-[1,1-bis(4-hydroxyphenyl)ethyl]benzene,tris(hydroxyphenyl)methanes and these compounds having methyl group asthe substituent; mercaptoxazole; mercaptobenzoxazole; mercaptoxazoline;mercaptobenzothiazole; benzoxazoline; benzothiazolone;mercaptobenzimidazole; urazole; thiourazole; mercaptopyrimidine;imidazolone; and derivatives of these compounds.

[0055] As the auxiliary agent for improving the resolution and thefraction of the residual film, the photoresist composition of thepresent invention may further comprise isocyanurate-based compounds.Examples of the isocyanurate-based compound include1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-diethylbenzyl) isocyanurate and1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate.

[0056] Where necessary, the photoresist composition of the presentinvention may further comprise additives compatible with the compositionsuch as additional resins, plasticizers, stabilizers and surfactantswhich are conventionally used for improving the properties of the resistfilm.

[0057] The organic solvent used in the resist composition is notparticularly limited and a conventional solvent for photoresists can beused. Examples of the organic solvent include linear chain ketones suchas acetone, methyl ethyl ketone, cyclopentanone, 2-hexanone, 3-hexanone,2-heptanone, 3-heptanone, 4-heptanone, 2-octanone, 3-octanone and4-octanone; alcohols such as n-propyl alcohol, isopropyl alcohol,n-butyl alcohol and cyclohexanol; ethers such as ethylene glycoldimethyl ether, ethylene glycol diethyl ether and dioxane; alcoholethers such as ethylene glycol monomethyl ether and ethylene glycolmonoethyl ether; esters such as propyl formate, butyl formate, propylacetate, butyl acetate, methyl propionate, ethyl propionate, methylbutyrate, ethyl butyrate, methyl lactate and ethyl lactate; cellosolveesters such as cellosolve acetate, methylcellosolve acetate,ethylcellosolve acetate, propylcellosolve acetate and butylcellosolveacetate; propylene glycols such as propylene glycol, propylene glycolmonomethyl ether, propylene glycol monomethyl ether acetate, propyleneglycol monoethyl ether acetate and propylene glycol monobutyl ether;diethylene glycols such as diethylene glycol monomethyl ether,diethylene glycol monoethyl ether, diethylene glycol dimethyl ether,diethylene glycol diethyl ether and diethylene glycol methyl ethylether; saturated γ-lactones such as γ-butyrolactone, γ-valerolactone,γ-caprolactone and γ-caprylolactone; halogenated hydrocarbons such astrichloroethylene; aromatic hydrocarbons such as toluene and xylene; andpolar solvents such as dimethylacetamide, dimethylformamide andN-methylacetamide. The solvent may be used singly or in combination oftwo or more. The amount of the solvent is not particularly limited aslong as the amount is sufficient for homogeneously dissolving oruniformly dispersing the components described above.

[0058] The insulation film for organic EL devices of the presentinvention is an insulation film which is formed by heating a resist filmhaving a desired pattern and formed with the photoresist compositiondescribed above on a substrate in accordance with photolithography andhas a sectional shape having upper edge portions having a round shapeand the width increasing towards the bottom portion. It is preferablethat the area of the portion of the pattern contacting the substrateobtained after being heated is 140% or smaller of the corresponding areabefore being heated. When the downward increase in the sectional width[the area of the portion contacting the substrate relative to thecorresponding area before being heated, (%)] exceeds 140%, theinsulation film having the desired shape and the desired thickness isnot obtained, occasionally. When the downward increase in the sectionalwidth is small and the sectional shape before being heated is arectangle or close to a rectangle, the desired sectional shape havingthe width increasing towards the bottom portion is not obtained,occasionally. From the standpoints described above, it is preferablethat the downward increase in the sectional width is greater than 100%and 140% or smaller and more preferably in the range of 102 to 130%.

[0059] The thickness of the insulation film is, in general, in the rangeof 0.3 to 3 μm, more preferably in the range of 0.5 to 2 μm and mostpreferably in the range of 1 to 1.5 μm.

[0060]FIG. 3 shows a diagram exhibiting an example of the change in theshape when the resist film formed in accordance with thephotolithography is heated in the preparation of the insulation film ofthe present invention. The portion surrounded by the solid line shows afront view of the resist film having a rectangular sectional shape. Theportion surrounded by the broken line shows a front view of theinsulation film of the present invention obtained after heating theabove resist film. The downward increase in the sectional width is givenby 100×(b/a)².

[0061] As the substrate on which the insulation film for organic ELdevices of the present invention is formed, a transparent substratehaving a patterned transparent electrode layer (the anode) can be used.

[0062] As the transparent substrate, a flat and smooth substrate havinga transmittance of light in the visible region of 400 to 700 nm of 50%or greater is preferable. Examples of the transparent substrate includeglass plates and polymer plates. Examples of the glass plate includeplates of soda lime glass, glass containing barium and strontium, leadglass, aluminosilicate glass, borosilicate glass, barium borosilicateglass and quartz. Examples of the polymer plate include plates ofpolycarbonates, acrylic resins, polyethylene terephthalate, polyethersulfite and polysulfone. Among these transparent substrates, in general,glass plates are preferable.

[0063] As the anode, a transparent electrode using a metal, an alloy, anelectrically conductive compound or a mixture of these materials whichhas a great work function (4 eV or greater) as the electrode material ispreferable. It is preferable that the sheet resistance of the anode isseveral hundred Ω/cm² or smaller. Examples of the anode includeelectrodes using an electrically conductive material such as ITO (indiumtin oxide), SnO₂, ZnO and In—Zn—O as the electrode material. For formingthe anode, the electrode material is formed into a thin film inaccordance with the vapor deposition or the sputtering. The thickness ofthe anode is selected, in general, in the range of 10 nm to 1 mm andpreferably in the range of 10 to 200 nm although the thickness dependson the type of the material.

[0064] The insulation film for organic EL devices of the presentinvention described above can be efficiently produced in accordance withthe process of the present invention shown in the following.

[0065] In the process of the present invention, a resist film having asubstantially rectangular sectional shape and a desired pattern isformed with the photoresist composition described above on a substratewhich is specifically a transparent substrate having a patternedtransparent electrode layer (the anode) in accordance with thephotolithography. The formed resist film is heated at a temperaturehigher than the temperature of heat resistance of the resist film sothat the thermosetting component of component (C) in the resist film iscured. The insulation film for organic EL devices of the present havinga sectional shape which has upper edge portions having a round shape andthe width increasing towards the bottom portion can be obtained in thismanner.

[0066] The process for producing the insulation film will be describedspecifically in the following.

[0067] A transparent substrate having a patterned transparent electrodelayer (the anode) is coated with the photoresist composition describedabove using a spinner or the like and the formed coating layer is driedto form a photoresist layer. The thickness of the photoresist layer iscontrolled so that the completed insulation film has the prescribedthickness. The resultant laminate is irradiated with ultraviolet light,deep UV or excimer laser beams by an apparatus for exposure withdemagnified projection via a desired mask pattern or is subjected to thepattern drawing with electron beams. The treated laminate is thenheated. The heated laminate is developed with a developing liquid suchas an alkaline aqueous solution which is, for example, a 1 to 10% byweight aqueous solution of tetramethylammonium hydroxide and a resistfilm having the desired pattern and a substantially rectangularsectional shape is formed.

[0068] The resist film formed as described above is heated at atemperature higher than the temperature of heat resistance of the resistfilm by preferably 5° C. or greater and more preferably by 10° C. orgreater so that the thermosetting component in the resist film is cured.It is important that the temperature of the heating is controlled inaccordance with the temperature of heat resistance of the resist filmand the temperature of starting the curing of the thermosettingcomponent so that the insulation film having a sectional shape havingupper edge portions having a round shape and the width increasingtowards the bottom portion is formed.

[0069] It is preferable that the temperature of heat resistance of theresist film is in the range of 90 to 130° C. and more preferably in therange of 95 to 125° C. When the temperature of heat resistance of theresist film is in the above range and a thermosetting imide resin suchas bisallylnadimide is used as the thermosetting component, it ispreferable that the temperature of heating the resist film is in therange of 140 to 250° C. and more preferably in the range of 150 to 200°C. The time of the heating is varied depending on the temperature of theheating and cannot be generally decided. In general, the time of theheating in the range of about 60 to 30 seconds is sufficient.

[0070] The insulation film for organic EL devices of the presentinvention can be efficiently obtained as described above. Since theresist film has been treated by heating at a high temperature, volatilecomponents in the film have been removed almost completely and do notadversely affect the organic EL device.

[0071] The present invention also provides the organic EL device havingthe resist film prepared as described above.

[0072] An embodiment of the process for producing the organic EL deviceof the present invention will be described in the following.

[0073] As described above, a resist pattern layer is formed inaccordance with a conventional process via the insulation film of thepresent invention which is formed on the transparent substrate havingthe patterned transparent electrode (the anode) and has the sectionalshape having the width increasing towards the bottom portion. The resistpattern layer may have a rectangular sectional shape or a undercutpattern profile.

[0074] When the resist pattern layer having a rectangular sectionalshape is formed, the photoresist used for forming the layer may be anyof the non-chemical amplification type and the chemical amplificationtype and may be any of the positive type and the negative type. Examplesof the photoresist include (1) positive-type photoresists of thenon-chemical amplification type which comprise a novolak resin solublein an alkali and a compound having quinonediazide group as the essentialcomponents, (2) positive-type photoresists of the chemical amplificationtype which comprise a resin exhibiting change in solubility in an alkaliby the action of an acid and a compound generating an acid byirradiation with a radiation as the essential components, and (3)negative type photoresists of the chemical amplification type whichcomprise a resin soluble in an alkali, a substance crosslinked with anacid and a compound generating an acid by irradiation with a radiationas the essential components.

[0075] When the resist pattern layer having a undercut pattern profileis formed, a photoresist such as that described in Japanese Patent No.2989064 can be used. Examples of this photoresist include a negativetype photoresist which comprises at least one of (A) a componentcrosslinked by exposure to light or by exposure to light, followed by aheat treatment, (B) a resin soluble in an alkali and (C) a compoundwhich absorbs the light used for the exposure, and is developed by analkaline aqueous solution.

[0076] The process for forming the resist pattern layer using the abovephotoresist is not particularly limited and the resist pattern layerhaving the rectangular sectional shape or the undercut pattern profilecan be formed in accordance with the conventional lithography. Thethickness of the resist pattern layer is, in general, about 0.5 toseveral μm.

[0077] After the resist pattern layer is formed on the transparentsubstrate having the patterned transparent electrode layer via theinsulation film of the present invention as described above, a holeinjecting and transporting layer is formed in accordance with the vacuumvapor deposition. The conditions for the vacuum vapor deposition aredifferent depending on the used compound (the material of the holeinjecting and transporting layer) and the crystal structure and therecombination structure of the hole injecting and transporting layer tobe formed. In general, it is preferable that the conditions are suitablyselected in the following ranges: the temperature of the source of vapordeposition: 50 to 450° C.; the degree of vacuum: 1×10⁻⁵ to 1×10⁻¹ Pa;the rate of vapor deposition: 0.01 to 50 nm/sec; the temperature of thesubstrate: −50 to 300° C.; and the thickness of the layer: 5 nm to 1 μm.

[0078] In the next step, an organic light emitting layer is formed onthe hole injecting and transporting layer in accordance with the vacuumvapor deposition. In general, the conditions for the vacuum vapordeposition can be selected in the same ranges as those described for theformation of the hole injecting and transporting layer although theconditions are different depending on the compounds used for the vacuumvapor deposition. It is preferable that the thickness of the layer is inthe range of 10 to 40 nm.

[0079] On the light emitting layer thus formed, an electron injectinglayer is formed in accordance with the vacuum vapor deposition. Theconditions for the vacuum vapor deposition can be selected in the sameranges as those described for the formation of the hole injecting andtransporting layer and the formation of the light emitting layer. It ispreferable that the thickness of the layer is in the range of 5 nm to 1μm.

[0080] As the final step, the cathode is laminated in accordance withthe vacuum vapor deposition. The cathode is composed of a metal. It ispreferable that the thickness of the cathode is in the range of 50 to200 nm.

[0081] A laminate (a light emitting portion) comprising the transparentelectrode layer (the anode), the organic EL material layer (the holeinjecting and transporting layer, the organic light emitting layer andthe electron injecting layer) and the metal electrode layer (thecathode) on the transparent substrate is formed as described above.

[0082]FIG. 4 shows a sectional view exhibiting the construction of anembodiment of the light emitting portion in the organic EL device of thepresent invention. On a transparent substrate 1 having a patternedtransparent electrode layer 2, resist pattern layers (resin separationlayers) 4 having a undercut pattern profile are disposed via theinsulation film of the present invention 3′ having the sectional shapehaving the width increasing towards the bottom portion. Between theresist pattern layers, an organic EL material layer 5 (having theconstruction in which a hole injecting and transporting layer, anorganic light emitting layer and an electron injecting layer aresuccessively formed from the side of the transparent electrode layer)having a metal electrode layer 6 on the surface is disposed and a lightemitting portion is formed. On the resist pattern 4, an organic ELmaterial layer 5 a having a metal electrode layer 6 a is formed due toconvenience in the preparation although the organic EL material layer 5a is not necessary from the standpoint of the function.

[0083] Since the insulation film 3′ has, as shown in FIG. 4, the shapehaving the width increasing towards the bottom portion in the aboveorganic EL device, attachment of the metal electrode material to thetransparent electrode layer 2 due to the extended deposition of themetal electrode material can be prevented during the lamination of themetal electrode layer 6 in accordance with the vacuum vapor deposition.Therefore, undesirable phenomena such as short circuit do not takeplace.

[0084] In addition to the above application of the insulation film ofthe present invention to the organic EL device, the insulation film ofthe present invention can also be used as a bank comprising aninsulation film disposed between holes in organic EL devices which areobtained by forming organic EL material layers by injecting amacromolecular organic EL material in accordance with the ink jetmethod.

[0085] In the above organic EL device, the organic light emitting layerhas the following functions: (1) the injecting function of injectingholes from the anode or the hole injecting and transporting layer andinjecting electrons from the cathode or the electron injecting layerunder application of an electric field; (2) the transporting function oftransporting the injected charges (electrons and holes) by the force ofthe electric field; and (3) the light emitting function of providing thefield for recombination of electrons and holes within the light emittinglayer and leading the recombination to light emission. The type of thelight emitting material used in the light emitting layer is notparticularly limited and a material conventionally used as the lightemitting material in organic EL devices can be used. Examples of thelight emitting material include fluorescent whitening agents such asbenzothiazole-based agents, benzimidazole-based agents andbenzoxazole-based agents; metal chelate oxinoid compounds;styrylbenzene-based compounds; distyrylpyrazine derivatives; andaromatic dimethylidine compounds.

[0086] The hole injecting and transporting layer is a layer comprising ahole transporting compound and has the function of transporting holesinjected from the anode to the light emitting layer. By disposing thehole injecting and transporting layer between the anode and the lightemitting layer, a greater amount of holes are injected into the lightemitting layer under a lower electric field. Moreover, electronsinjected from the cathode or the electron injecting layer into the lightemitting layer are accumulated in the vicinity of the interface of thelight emitting layer and the hole injecting and transporting layer inthe light emitting layer due to the barrier for electrons existing atthe interface. Thus, the efficiency of light emission of the organic ELdevice is improved and the EL device exhibiting the excellent lightemitting property can be prepared. The hole transporting compound usedin the hole injecting and transporting layer is not particularly limitedand conventional compounds used heretofore as the hole transportingcompound in organic EL devices can be used. Example of the holetransporting compound include triazole derivatives, oxadiazolederivatives, imidazole derivatives, polyarylalkane derivatives,pyrazoline derivatives, pyrazolone derivatives, phenylenediaminederivatives, arylamine derivatives, amino-substituted chalconederivatives, oxazole derivatives, styrylanthracene derivatives,fluorenone derivatives, hydrazone derivatives, stilbene derivatives,silazane derivatives, polysilane derivatives, aniline-based copolymersand specific electrically conductive macromolecular oligomers such asthiophene oligomers.

[0087] The electron injecting layer has the function of transportingelectrons injected from the cathode to the organic light emitting layer.The electron transporting compound used in the electron injecting layeris not particularly limited and conventional compounds used heretoforeas the electron transporting compound in organic EL devices can be used.Example of the electron transporting compound include nitro-substitutedfluorenone derivatives, anthraquinodimethane derivatives,diphenylquinone derivatives, thiopyrane dioxide derivatives,heterocyclic tetracarboxylic acid anhydrides such as correspondingcompounds having naphthalene ring or perylene ring, carbodiimides,fluorenylidene-methane derivatives, anthrone derivatives, oxadiazolederivatives and metal complexes of 8-quinolinol and derivatives thereof.Examples of the metal complex of 8-quinolinol and the derivative thereofinclude tris(8-quinolinol)aluminum, bis(8-quinolinol)magnesium,bis(benzo-8-quinolinol)zinc, bis(2-methyl-8-quinolylato)aluminum oxide,tris(8-quinolinol)indium, tris(5-methyl-8-quinolinol)aluminum,8-quinolinollithium, tris(5-chloro-8-quinolinol)potassium,bis(5-chloro-8-quinolinol)potassium,tris(5,7-dichloro-8-quinolinol)aluminum,tris(5,7-dibromo-8-quinolinol)aluminum, bis(8-quinolinol)beryllium,bis(2-methyl-8-quinolinol)beryllium, bis(8-quinolinol)zinc,bis(2-methyl-8-quinolinol)zinc, bis(8-quinolinol)tin andtris(7-propyl-8-quinolinol)aluminum.

[0088] The organic light emitting layer, the hole injecting andtransporting layer and the electron injecting layer may be constitutedwith a single layer comprising at least one material for the layer ormay be a laminate of at least two layers each comprising differentmaterials.

[0089] As the cathode, a metal electrode comprising a metal, an alloy,an electrically conductive compound or a mixture of these materialswhich has a small work function (4 eV or smaller) as the electrodematerial is used. Examples of the electrode material include sodium,sodium-potassium alloys, magnesium, lithium, magnesium-silver alloys,aluminum/aluminum oxide, indium and rare earth metals. It is preferablethat the sheet resistance as the electrode is several hundred Ω/cm² orsmaller.

EXAMPLES

[0090] The present invention will be described more specifically withreference to examples in the following. However, the present inventionis not limited to the examples.

Example 1 Preparation of Positive-Type Resist (A-1)

[0091] A novolak resin having a weight-average molecular weight of5,500, which was obtained by condensation of a mixed cresol containingm-cresol and p-cresol (the ratio of the mounts by weight: 50/50) andformaline in the presence of oxalic acid as the catalyst, in an amountof 100 parts by weight, 22 parts by weight of1,2-naphthoquinonediazide-4-sulfonic acid ester of2,3,4-trihydroxybenzophenone (the fraction of esterification: 67% bymole), 5 parts by weight of a thermosetting imide resin “BANI-M” [atrade name; manufactured by MARUZEN SEKIYU KAGAKU Co., Ltd.] and 450parts by weight of polyethylene glycol monomethyl ether acetate (PGMEA)were mixed. After the components were completely dissolved, theresultant solution was filtered through a membrane filter made ofpolytetrafluoroethylene having pores having a diameter of 0.5 μm[manufactured by MILLIPORE Company] and positive-type resist (A-1) wasprepared.

Example 2 Preparation of Positive-Type Resist (A-2)

[0092] To positive-type resist (A-1) obtained in Example 1, 30 parts byweight (as pure titanium black) of titanium black treated for dispersionwith a polyester-based dispersant and 106 parts by weight of PGMEA per100 parts by weight of the novolak resin in resist (A-1) were mixed. Thecomponents were completely uniformly dispersed and positive-type resist(A-2) was prepared.

Comparative Example 1 Preparation of Positive-Type Resist (A-3)

[0093] A novolak resin having a weight-average molecular weight of5,500, which was obtained by condensation of a mixed cresol containingm-cresol and p-cresol (the ratio of the amounts by weight: 50/50) andformaline in the presence of oxalic acid as the catalyst, in an amountof 100 parts by weight, 22 parts by weight of1,2-naphthoquinonediazide-4-sulfonic acid ester of2,3,4-trihydroxybenzophenone (the average fraction of esterification:67% by mole) and 430 parts by weight of PGMEA were mixed. After thecomponents were completely dissolved, the resultant solution wasfiltered through a membrane filter of polytetrafluoroethylene havingpores having a diameter of 0.5 μm [manufactured by MILLIPORE Company]and positive-type resist (A-3) was prepared.

Test Example

[0094] Positive-type resist (A-1) obtained in Example 1, positive-typeresist (A-2) obtained in Example 2 and positive-type resist (A-3)obtained in Comparative Example 1 were each applied to a transparentglass substrate using a spin coater each in an amount such that theformed coating film had a thickness of 1.0 μm after being dried. Theprepared films were heated on a hot plate at 100° C. for 90 seconds andphotoresist layers were formed.

[0095] The formed photoresist layers were exposed to light having anenergy of 120 mJ/cm² using a light exposure apparatus “PLA501F”[manufactured by CANON Co., Ltd.] via a mask to obtain latent images.The exposed photoresist layers were treated by the paddle development ina 2.38% by weight aqueous solution of tetramethylammonium hydroxide for60 seconds and resist films having a substantially rectangular sectionalshape were formed.

[0096] The photoresist films were then heated on a hot plate at thetemperature shown in Table 1 for 180 seconds and insulation films havinga sectional shape having the width increasing towards the bottom portionwere prepared. The downward increase in the sectional width [100×(b/a)²,%] was obtained by using pictures of a scanning electron microscope(SEM). The results are shown in Table 1. TABLE 1 Positive-type Downwardincrease in the sectional width resist 150° C. 200° C. 250° C. Example 1(A-1) 104% 125% 128% Example 2 (A-2) 108% 117% 114% Comparative 149%219% — Example 1 (A-3)

[0097] As shown in Table 1, the insulation films of Examples 1 and 2 hadmuch smaller downward increases in the sectional width than that of theinsulation film of Comparative Example 1.

[0098] Upper edge portions of all insulation films had a round shape.The specific permittivity measured in accordance with the method ofJapanese Industrial Standard C6481 was in the range of 3.3 to 3.5.

Example 3

[0099] (1) Preparation of an Insulation Film

[0100] A glass substrate of a size of 25×75×1.1 mm which had on thesurface a patterned ITO transparent electrode having a thickness of 120nm was coated with positive-type resist (A-2) obtained in Example 2using a spin coater in an amount such that the formed film had athickness of 1.0 μm after being dried. The coating film was heated on ahot plate at 100° C. for 90 seconds and a resist layer was formed.

[0101] The formed resist layer was exposed to light having an energy of120 mJ/cm² using a light exposure apparatus “PLA501F” used above via amask having a desired pattern to obtain a latent image. The exposedresist layer was treated by the paddle development in a 2.38% by weightaqueous solution of tetramethylammonium hydroxide for 60 seconds. Thedeveloped resist layer was heated on a hot plate at 200° C. for 180seconds and an insulation film having a sectional shape having the widthincreasing towards the bottom portion, in which the downward increase inthe sectional width was 117%, and a thickness of 1.0 μm was prepared.

[0102] (2) Formation of a Resist Pattern Having a Undercut PatternProfile

[0103] A novolak resin having a weight-average molecular weight of5,200, which was obtained by polycondensation of a mixed cresolcontaining m-cresol and p-cresol (the ratio of the amounts by weight:60/40) with formaldehyde, in an amount of 100 parts by weight, 10 partsby weight of hexamethoxymethylated melamine, 3 parts by weight of2-(4-methoxy-naphthel)-4,6-bis(trichloromethyl)-s-triazine and 3 partsby weight of 4-(4-dimethylaminophenylazo)phenol were dissolved in 300parts by weight of ethylcellosolve acetate. The resultant solution wasfiltered through a membrane filter and a photosensitive composition wasprepared.

[0104] The glass substrate having the insulation film obtained in (1)was coated with the above composition in accordance with the spincoating. The formed coating film was heated on a hot plate at 90° C. for60 seconds and a resist film having a thickness of 1.5 μm was formed.

[0105] The resist film was exposed to light using the light exposureapparatus “PLA501F” used above via a mask having a desired pattern andtreated by the paddle development in a 0.5% by weight aqueous solutionof NaOH for 60 seconds. Due to the above operation, a resist patternhaving a undercut pattern profile was formed on the insulation film. Theresist pattern was irradiated with light by using a high pressuremercury lamp having a brightness at 254 nm of 1.2 mW/cm² for 200 secondsto bake the resist pattern and a member for an organic EL device wasprepared.

[0106] (3) Preparation of an Organic EL Device

[0107] The member for an organic EL device prepared in (2) describedabove was used as the substrate and fixed at a substrate holder of acommercial vapor deposition apparatus [manufactured by NIPPON SHINKUGIJUTU Co., Ltd.]. Into a boated made of molybdenum and heated byresistance, 200 mg ofN,N′-bis(3-methylphenyl)-N,N′-diphenyl[1,1′-biphenyl]-4,4′-diamine(hereinafter, referred to as TPD) was placed and 200 mg of4,4′-bis(2,2′-diphenylvinyl)biphenyl (hereinafter, referred to as DPVBi)was placed into another boated made of molybdenum and heated byresistance. The vacuum chamber was evacuated to 1×10⁻⁴ Pa.

[0108] TPD was vapor deposited at a rate of vapor deposition of 0.1 to0.3 nm/sec by heating the boat containing TPD at 215 to 220° C. and ahole injecting and transporting layer having a thickness of 60 nm wasformed. During this formation, the temperature of the substrate was keptat the room temperature. Without taking out the coated substrate, DPVBiwas vapor deposited on the formed hole injecting and transporting layerat a rate of vapor deposition of 0.1 to 0.3 nm/sec by heating the boatcontaining DPVBi at 240° C. and a light emitting layer having athickness of 40 nm was formed. During this formation, the temperature ofthe substrate was kept at the room temperature.

[0109] The resultant product was taken out of the vacuum chamber. Aftera mask made of stainless steel was placed on the light emitting layerformed above, the product was fixed at the substrate holder again. Intoa boat made of molybdenum, 200 mg of tris(8-quinolinol)aluminum(hereinafter, referred to as Alq₃) was placed and 1 g of magnesiumribbon was placed into another boat made of molybdenum. Into a basketmade of tungsten, 500 mg of silver wire was placed. The boats and thebasket were placed into the vacuum chamber.

[0110] After the vacuum chamber was evacuated to 1×10⁻⁴ Pa, Alq₃ wasvapor deposited on the light emitting layer formed above at a rate ofvapor deposition of 0.01 to 0.03 nm/sec by heating the boat containingAlq₃ at 230° C. and an electron injecting layer having a thickness of 20nm was formed. On the formed electron injecting layer, silver was vapordeposited at a rate of vapor deposition of 0.1 nm/sec and,simultaneously, magnesium was vapor deposited at a rate of vapordeposition of 1.4 nm/sec. Thus, a cathode composed of a mixed metal ofmagnesium and silver and having a thickness of 150 nm was formed and alight emitting portion of an organic EL device shown in FIG. 4 wasformed.

[0111] Then, a sealing layer was formed in accordance with theconventional process and an organic EL device was prepared.

[0112] When a direct current was applied to the device using the ITOfilm as the anode and the mixed metal film as the cathode, emission ofblue light could be recognized in a bright environment under a voltageof 5 V or greater and the self-distinguishability was found to be veryexcellent.

INDUSTRIAL APPLICABILITY

[0113] The photoresist composition of the present invention comprises athermosetting component which is cured at a specific temperature andprovides the insulation film which has a sectional shape having upperedge portions having a round shape and the width increasing towards thebottom portion and is advantageous as the insulation film for organic ELdevices.

[0114] By using the above insulation film, the organic EL device can beproduced with stability and suppressed formation of defect products.

What is claimed is:
 1. A photoresist composition for forming aninsulation film for organic electroluminescence devices which comprises(A) a resin soluble in an alkali, (B) an ester of aquinonediazidesulfonic acid, (C) a thermosetting component which iscured at a temperature higher than a temperature of heat resistance of aresist film formed with the composition in accordance withphotolithography, and an organic solvent.
 2. A photoresist compositionfor forming an insulation film according to claim 1, wherein thethermosetting component of component (C) is a thermosetting imide resinrepresented by general formula [1]:

wherein R represents a group expressed by:

representing an integer of 3 to
 8. 3. A photoresist composition forforming an insulation film according to claim 1, which comprises 1 to 20parts by weight of component (C) per 100 parts by weight of component(A).
 4. An insulation film for organic electroluminescence devices whichis formed by heating a resist film having a desired pattern and formedwith a composition described in claim 1 on a substrate in accordancewith photolithography, has a sectional shape having upper edge portionshaving a round shape and a width increasing towards a bottom portion andhas a thickness in a range of 0.3 to 3 μm.
 5. A process for producing aninsulation film for organic electroluminescence devices described inclaim 4, the process comprising forming a resist film having asubstantially rectangular sectional shape and a desired pattern with aphotoresist composition described in claim 1 on a substrate inaccordance with photolithography and heating the formed resist film at atemperature higher than a temperature of heat resistance of the resistfilm so that the thermosetting component in the resist film is cured. 6.An organic electroluminescence device which comprises an insulation filmdescribed in claim 4.